Way about a few years ago I tried running a play-by-post game (back on the Groovy Gamers forum before that place got all weird) with disastrous results. I've gotten the itch again (mostly to fill my need for some M&M gaming), but I don't want to set myself --and the players who are willing to get invested in my game-- up for failure. Obviously there's a lot of PBP gaming going on in the Gaming Room forum that I've perused for ideas, but if anyone had any suggestions on structure, types of adventures that work best, or anything at all about running a PBP game, I'd appreciate it.

I found that PBP games need to have more plot structure than in person or real time ones. When the players and GM can talk immediately its easier to do things like get a group together, go off on small tangent plots on the whim of a few players, and generally mix things up from a pre thought-out plot. In PBP players don't have that instantaneous communication, so if the players steer the game in a strange direction by their actions its harder to get everyone back on track.

Pacing is also important in PBP games. As a GM you need to post three times more on average than the players I found to answer all their queries, say what the NPC's are doing, running combat, and other things a live game can dispatch with quickly. A simple question such as "What does the woman look like?" could take two days or more to resolve with some action based on the information. In the same vein, you need to keep an eye out for when the character talking dies down so you can move the game along.

You need to be able to adjust to players dropping or getting really busy fairly easily. In PBP, unless you get all really dedicated players, there will probably be people dropping every few months if not more frequently. In one game I ran here a player dropped after two days.

Story telling and description in your GM posts are especially important. If it is too vague, the players will take a long time to fully get a sense of the situation due to the communication delay. A good description allows the players to easily know most of the details in an engaging post.

You need to make sure the players are mature. In a live game an annoying player can be handled quickly and players have more of a stake due to the person to person contact. A PBP game on a forum with a lot of games means that if there is an annoying player and the others get too annoyed, they will leave the game and go another fairly easily. You also probably wouldn't have the same level of investment as you would GMing a live game.

The only thing I would add to MrDent's advise is that you should let the mature players fill in some of the fluff.

You don't need to generate every scene down to the last detail, and you don't need to generate personality for every NPC they might interact with. Mature players will add in some fluff to the environment to show some characterization. Draw the line at letting them add actual encounters to the story. But let them "see" a poster on the wall and react a certain way to it when you never planned for a poster to be there. Or letting them "see" head-banger in the random crowd so some phobia can be shown that has gone otherwise unseen. These are good ways to have the players feel more of a personal stake in the game.